1. Field
The present disclosure relates to power management for electronic devices which are coupled together. More specifically, the present disclosure relates to coordination of power sources between a host device and an accessory device.
2. Related Art
The capabilities offered by a portable electronic device may be expanded by coupling it to another portable electronic device. For example, a host device, such as a cellular telephone, may be coupled to an accessory device, such as a credit-card reader, and the combination of the two may allow payment using a credit or debit card at an arbitrary location.
However, in this configuration the power usage of the host device and the accessory device are not coordinated. Because each of these devices has a separate power source (such as a battery) with a different amount of available power, in general the operating life of the host device and the accessory device are likely to be different. As a consequence, one of the devices may run out of power before the other, in which case the additional capabilities offered by the combination of the host device and the accessory device will no longer be available.
Hence, what is needed is a technique for coordinating the power sources in the host device and the accessory device that overcomes the problems listed above.